Problem: You have a list of airline tickets as pairs [from, to]. Reconstruct the itinerary starting from "JFK". If multiple valid itineraries exist, return the lexicographically smallest one.
Link: LeetCode 332
Example:
- Input: [["JFK","SFO"],["JFK","ATL"],["SFO","ATL"],["ATL","JFK"],["ATL","SFO"]]
- Output: ["JFK","ATL","JFK","SFO","ATL","SFO"]
Note: You must use all tickets exactly once. This is an Euler path with a twist.